A video streaming server is a device that is capable of streaming hundreds to thousands of video streams to Set Top Boxes at customer premises. The content itself may reside on CD's, conventional rotating disks, flash disks or even RAM. The most used storage today is conventional disks because of its low price per data volume.
Streaming video requires a precise timing regarding the point in time a specific frame is sent relative to the previous one. Further, it requires a precise timing regarding the point in time each packet belonging to that frame is sent. One frame contains one or several packets depending on the amount of data to be transmitted in the frame. If frames are not sent timely, the video buffer in the Set Top Box will either overflow or underflow. Further, if packets are not sent timely, the subscriber line, for instance ADSL, will be over-utilized thereby violating the service level agreement which would in most cases result in a packet loss.
Streaming in order of thousands of streams concurrently puts high demand on the scheduler who selects what frame or packet to send at a specific point in time.
Scheduling by using calendar wheels has been applied in a diverse of fields. For instance ATM scheduling is common practice.
According to prior art U.S. Pat. No. 6,477,168 Cell/frame scheduling method and communications cell/frame scheduler, Delp et al, there is described a method and apparatus for scheduling the transmission of cells and frames in a communications network. The transmission of cells and frames are scheduled utilizing a selected scheduling algorithm. The cell/frame scheduling algorithm includes the step of identifying a frame or cell transmission type. Responsive to the identified frame or cell transmission type, a frame multiplier value is identified and used to calculate a target transmission time. The main purpose is to have a scheduling with respect to quality and bandwidth. The patent does not discuss streaming hundreds or thousands of video streams to Set Top Boxes.